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QSIG
B Private Networking
Path Retention
Path Retention is a generic mechanism for retaining a network connection that can be
used by supplementary services during call establishment.
The Originating PBX invokes path retention for one supplementary service or for
several simultaneous supplementary services. Invoking a particular supplementary
service means retaining the network connection if the Terminating PBX encounters
the appropriate conditions. The Originating PBX is informed of the reason for
retaining the connection. It then decides (for example, by consulting the calling user)
whether to invoke the supplementary service. Under some circumstances in which the
network connection is retained, more than one of the supplementary services for
which path retention has been invoked may be applicable.
Successive retentions of the network connection by the Terminating PBX following a
single path-retention invocation by the Originating PBX are possible. This is a result
of different conditions being encountered at the Terminating PBX. When an attempt
is made to invoke a supplementary service for which the network connection has been
retained, a further condition can be encountered that can cause the network
connection to be retained again for the same or a different supplementary service.
Path retention is specified in terms of a Path Retention entity existing within the
Coordination Function at the Originating PBX and at the Terminating PBX.
QSIG Centralized Attendant Services
QSIG Centralized
Attendant Service
(QSIG-CAS)
DEFINITY ECS supports two versions of CAS: RLT-CAS and QSIG-CAS.
The CAS feature enables one or more Branch PBXs to concentrate their attendants on
one Main PBX. CAS provides transparency between PBXs of most features that are
normally available to the basic attendant service.
RLT-CAS uses an analog RLT network to optimized trunk utilization. QSIG-CAS
does not use RLT. By using QSIG Transfer and QSIG Path Replacement or QSIG
Diversion with Rerouting, the same optimization as using RLT can be accomplished
with QSIG-CAS. Using QSIG CAS, you eliminate the need to have a separate analog
RLT network.
All current QSIG features and RLT-CAS features are available with QSIG-CAS.
Potential Drawbacks
There are a few potential drawbacks when using QSIG-CAS:
1 Unlike RLT, QSIG Path Replacement does not work immediately. This means
that resources are being utilized longer during QSIG-CAS as opposed to
RLT-CAS.
2 Unlike RLT, QSIG Path Replacement is not guaranteed.
3 Like RLT, QSIG Path Replacement does not enable a branch PBX to act as a
gateway PBX.
4 No path replacement functionality takes place during or after a conference.
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Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000